IC Usage Notes
1. About the local oscillator
Fig. 1 shows the equivalent circuit for the local oscillator.
In this circuit, when C1 = 22 pF, the change in the negative resistance versus C2 is shown in Fig. 2, the change in the operational
load capacitance is shown in Fig. 3, and the frequency deviation is shown in Fig. 4. In the application circuit,
C2 = 120 pF, and in this case the negative resistance according to Fig. 2 is –58 Ω. In order to increase the negative resistance, it is
necessary to decrease the value of C2. To increase the oscillation level, it is possible to add external resistor R1 and raise the local
oscillator current. However, the oscillation level on pin 1 must be set to 110 dB or less. If set to a greater level, distortion will
occur in the oscillation waveform.
Fig 2 to 4: C1 = 22 pF
Figs. 3, 4: Reference to operating load
capacitance 16 pF
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